Mechanical filter-based pollution control system to remediate cooking emissions

ABSTRACT

A mechanical filter-based air pollution control system for removing particle and gas phase pollutants in a waste airstream exhausted from commercial cooking operations is described, which includes a housing enclosing at least three filter stages to remove particle and gas pollutants in the airstream. The example system may include a fogger assembly that sprays fog droplets into the waste airstream to condense a portion of gas phase pollutants into condensed particles, a wash mechanism including spray nozzles to wash surfaces of the first stage filter to remove grease therefrom, and injection means for injecting activated ozone, which comprises ozone with a surplus of hydroxyl radicals, into the housing to initiate advanced oxidation processes (AOPs) to decompose particle and gas phase pollutants within the waste airstream in the filters. Where activated ozone is employed, the system includes a fourth stage filter that adsorbs and retains gas phase pollutants for subsequent oxidation.

CROSS-REFERENCE TO RELATED APPLICATION

The present application claims the benefit under 35 U.S.C. §119(e) ofU.S. Provisional Patent Application No. 61/827,191 to the inventor,filed May 24, 2013, the entire contents of which is hereby incorporatedby reference herein.

BACKGROUND

1. Field

Example embodiments in general relate to a mechanical filter-basedpollution control system to remediate cooking emissions.

2. Related Art

The emission profile from commercial cooking operations has been wellstudied and shown to consist of particles (aerosols), semi-volatileorganic compounds (sVOCs), volatile organic compounds (VOCs) andinorganic volatile species. The particles give rise to visual smoke andthe VOCs give rise to odors.

The mass, size distribution and organic chemistry profile of theemissions can vary widely and are functions primarily of the type ofcooking apparatus and the chemical and structural composition of the rawfood being cooked. The most severe challenge to cooking emissionremediation has been demonstrated repeatedly to be the emissionsgenerated by gas char broiling of ground beef patties, with the severityof emissions being proportionately related to the fat content and thedegree of well doneness of the beef patties. Of particular note is thatthe aerosol and chemical profiles of char broiled ground beef have beencharacterized and shown to not be dissimilar from the emission profileof diesel exhaust. Of particular concern are the National Ambient AirQuality Standards (NAAQS) and EPA Title V air toxics that are released.These include but are not limited to: PM2.5, PAH (poly aromatichydrocarbons), butadienes, other toxic VOCs and ozone precursors.Indeed, air quality management districts in California are currently inthe process of generating cooking emission remediation standards forcharbroiling of beef, and the Bay Area Air Quality Management District(BAAQMD) has already promulgated such regulations.

Historically and currently, there are two established ways ofremediating the particulate (aerosol) cooking emissions: removal fromthe airstream by electrostatic deposition onto alternatively chargedplates or mechanical removal of the aerosols by passing the airstreamthrough a series of progressively more efficient media filters.Established known mechanical filtration properties include impaction,interception, and interference.

Both technologies have been proven to be highly effective and there areadvantages to choosing one over the other. The two main advantages ofelectrostatic precipitators have been first, that the pressure dropthrough the filters is 50-75% less than through clean mechanicalfilters, with that difference becoming more pronounced as the mechanicalfilters load. For an electrostatic precipitator the pressure dropremains constant, whereas, as mechanical filters load, the resistance toairflow increases, thus decreasing the total air that can be exhaustedin the kitchen hood. This is a concern for modern day low flow hoods.This condition often mandates a constant flow control system and/orfilter change warning mechanisms. Second is that the electrostaticprecipitators can be programmed for nightly washing, thus removing thegrease from the duct pathway and decreasing the risk of fire presentedby accumulated grease in the ducted system.

Mechanical filtration control devices are often favored because theytypically cost less and are more fail-safe in that electrical componentsare not required for proper functioning. Mechanical filters are alsoeasier to service because highly trained technicians are not requiredfor routing maintenance. These mechanical systems typically have threestages of progressively more efficient filters with the three stagestypically in the range (all efficiencies in MERV ratings):

-   1. STAGE 1—MERV 6-10,-   2. STAGE 2—MERV 12-15, and-   3. STAGE 3—(95-99) DOP up to HEPA (99.97) DOP, wherein the numbers    in parentheses represent percentage of 0.3 micrometer particles    removed.

A well established mode exists at 0.2 micrometer diameter aerosols forchar broiling beef, so the stage 3 filters are mandatory. These filtersare expensive so the correct selection of the workhorse filters of stage1 and stage 2 are paramount. The frequency of filter changing varieswith the cooking load; however, the optimal scenario would be a month'sduration for stages 1 and 2 and a quarterly duration for stage 3.

For both types of particulate control technologies, neither onesignificantly effects the removal of sVOCs or VOCs. This emissionscomponent is either ignored, or more often (especially when cooking odorabatement is desired) removed by adsorption (with varying success) by asorbent such as activated charcoal.

SUMMARY OF THE INVENTION

An example embodiment of the present invention is directed to amechanical filter-based air pollution control system for removingparticle and gas phase pollutants in a waste airstream exhausted fromcommercial cooking operations. The system includes a housing having aninlet and an outlet, an exhaust fan attached to the outlet for drawingthe waste airstream into the inlet and through the housing to the outletand discharged to the outside atmosphere, and a fogger assembly arrangedwithin the housing at the inlet and connected to a cold water source forspraying equal-sized 1 micrometer droplets to mix with the incomingwaste airstream so as to achieve psychrometric saturation of the wasteairstream, evaporative cooling of the airstream, and condensation of aportion of gas phase pollutants in the waste airstream into condensedparticles. The system includes a first stage metal filter arrangedwithin the housing and downstream of the fogger assembly for filteringparticle pollutants, and solubilizing and removing, by drainage, polarparticle and gas phase pollutants in the waste airstream, a second stagefilter arranged within the housing and downstream of the first stagefilter, the second stage filter including a wool layer attached to aMERV 15 synthetic media therein for removing particles, including thecondensed particles, and gas phase pollutants remaining in the wasteairstream after passing through the first stage filter, and a thirdstage filter arranged within the housing and downstream of the secondstage filter, the third stage filter including an oil-mist media thereinfor removing sub-micron particle including the condensed particlepollutants remaining in the waste airstream after passing through thesecond stage filter.

Another example embodiment is directed to a mechanical filter-based airpollution control system for removing particle and gas phase pollutantsin a waste airstream exhausted from commercial cooking operations. Thesystem includes a housing having an inlet and an outlet, an exhaust fanattached to the outlet for drawing the waste airstream into the inletand through the housing to the outlet, a disposable, synthetic firststage filter with an efficiency rating of MERV 6-10 for filteringparticles in the waste airstream, a second stage filter arranged withinthe housing and downstream of the first stage filter, the second stagefilter including a wool layer attached to a MERV 15 synthetic mediatherein for removing particle and gas phase pollutants remaining in thewaste airstream after passing through the first stage filter, and athird stage filter arranged within the housing and downstream of thesecond stage filter, the third stage filter including an oil-mist mediatherein for removing particle pollutants remaining in the wasteairstream after passing through the second stage filter. The systemfurther includes a fourth stage filter arranged within the housing anddownstream of the third stage filter for removing, by adsorption,sub-micron particle and gas phase pollutants remaining in the wasteairstream after passing through the third stage filter, and injectionmeans to inject activated ozone, which comprises ozone with a surplus ofhydroxyl radicals, within the housing to initiate advanced oxidationprocesses (AOPs) upon contact of the activated ozone with the wasteairstream so as to decompose particle and gas phase pollutants withinthe waste airstream and retained in the first through fourth stagefilters. The fourth stage filter quenches any fugitive or unused ozoneremaining in the system.

Another example embodiment is directed to a mechanical filter-based airpollution control system for removing particle and gas phase pollutantsin a waste airstream exhausted from commercial cooking operations. Thesystem includes a housing having an inlet and an outlet, an exhaust fanattached to the outlet for drawing the waste airstream into the inletand through the housing to the outlet and discharged to the outsideatmosphere, and a fogger assembly arranged within the housing at theinlet and connected to a cold water source for spraying fog droplets tomix with the incoming waste airstream so as to condense gas phasepollutants in the airstream to condensed particles. The system includesa first stage metal filter arranged within the housing and downstream ofthe fogger assembly for filtering particle pollutants, and solubilizingand removing, by drainage, polar particle and gas phase pollutants inthe waste airstream, a wash mechanism arranged in the housing in facingrelation to a front of the first stage filter, the wash mechanismincluding a manifold supporting a plurality of spray nozzles thereon,the manifold supplying a mix of heated water from a hot water source anddetergent to the nozzles for periodically washing surfaces of the firststage filter to remove grease therefrom, a second stage filter arrangedwithin the housing and downstream of the first stage filter for removingparticle and gas phase pollutants remaining in the waste airstream afterpassing through the first stage filter, and a third stage filterarranged within the housing and downstream of the second stage filterfor removing sub-micron particle including condensed particle pollutantsremaining in the waste airstream after passing through the second stagefilter. The system further includes a fourth stage filter arrangedwithin the housing and downstream of the third stage filter forremoving, by adsorption, condensed particles and gas phase pollutantsremaining in the waste airstream after passing through the third stagefilter, and injection means to inject activated ozone within thehousing, which comprises ozone with a surplus of hydroxyl radicals, toinitiate advanced oxidation processes (AOPs) upon contact of theactivated ozone with the waste airstream so as to decompose particle andgas phase pollutants within the waste airstream and retained in thefirst through fourth stage filters. The fourth stage filter quenches anyfugitive or unused ozone remaining in the system.

BRIEF DESCRIPTION OF THE DRAWINGS

Example embodiments will become more fully understood from the detaileddescription given herein below and the accompanying drawing, whereinlike elements are represented by like reference numerals, which aregiven by way of illustration only and thus are not limitative of theexample embodiments herein.

FIG. 1 is a block diagram of a pollution control system according to anexample embodiment.

FIG. 2 is a front portional view of part of the pollution control systemto show a fogger assembly in more detail.

FIG. 3 is a plan view of an example high pressure nozzle installed on acollar that is positioned on a stainless steel tube according to theexample embodiment.

FIG. 4 is a picture of a pump used for the fogger assembly according tothe example embodiment.

FIG. 5 is a front view of an ozone gas injection device according to anexample embodiment.

FIG. 6 is an end view of the ozone gas injection device of FIG. 5.

FIG. 7 is a partial side view of the first and second stage filters toillustrate the wash mechanism in greater detail.

FIG. 8 is a perspective view of the looping manifold and nozzles of thewash mechanism in relation to the first stage filter.

FIG. 9 is an example coil pack used in a stage I filter according to anexample embodiment.

FIG. 10 is another style of stage I filter according to an exampleembodiment.

FIG. 11 is a perspective view of a stage II filter according to anexample embodiment.

FIG. 12 shows a cross-section of the stage II filter of FIG. 11 toillustrate material components thereof.

FIG. 13 is a perspective front view of a stage III filter according toan example embodiment.

FIG. 14 is a cross-section of the stage III filter internals of FIG. 13.

FIG. 15 is a drawing of a recirculating (ventless) kitchen exhaust hood.

FIG. 16 is a side view of the drawing of FIG. 15.

FIG. 17 is a block diagram of a pollution control system according to anexample embodiment configured for the recirculating (ventless) kitchenexhaust hood of FIGS. 15 and 16.

FIG. 18 is a block diagram of a mechanical filter-based pollutioncontrol system according to another example embodiment.

DETAILED DESCRIPTION

In general, and as to be shown in further detail below, exampleembodiments are directed to a mechanical filter-based air pollutioncontrol system having a washable first stage filter that removesparticle pollutants such as grease and smoke, and gaseous odorouspollutants generated within a waste airstream from commercial cookingoperations by a commercial kitchen cooking ventilation hood. Thepollution control system incorporates novel and advanced chemical andphysical technologies either separately or in combination to achievemaximal removal efficiencies of these air pollutants.

As to be shown in more detail hereafter, the system includes a foggerassembly that is combined with a plurality of progressively moreefficient filters arranged within the system housing, including a stage1 reactor filter, a stage 2 combination wool/synthetic media layeredfilter, and a stage 3 oil-mist media filter that assimilates thecharacteristics and DOP ratings of a HEPA media filter, in an effort toachieve maximum removal of the total emissions from the waste airstreamwith minimal ongoing filter replacement cost. The system furtherincludes a wash mechanism provided for cleaning the stage 1 filter,thereby providing frequent and consistent grease removal from thefilter, while eliminating the need to frequently replace a disposabletype stage I filter. A disposable stage I filter is also available in analternative example embodiment.

Additionally, what is known as Advanced Oxidation Processes (AOPs)(which initiate when activated ozone (comprising ozone gas with asurplus of hydroxyl radicals (.OH)) is injected into the system to mixwith the emissions in the waste airstream) are utilized in combinationwith a proprietary synthetic hydrophobic zeolite sorbent serving as atleast part of an optional stage IV filter of the system, in an effort toachieve maximum removal, retention and subsequent decomposition of thegas phase odorous pollutants from the waste airstream.

FIG. 1 is a block diagram of a pollution control system according to anexample embodiment. As to be set forth more fully below, the exampleembodiments in general are directed to a mechanical filter-basedpollution control system (e.g., no electrostatic filtering) with washmechanism to remediate cooking emissions such as can be found in thewaste airstream emitted from a commercial kitchen cooking ventilationhood (not shown). The mechanical filter-based pollution control system100 of FIG. 1 features a wash mechanism 130 to effectively clean thefirst stage of mechanical filtration (stage I filter 120). The firststage filter 120 is selected due to its high efficiency and “washability”. Thus, one gains the benefit of nightly grease removal combinedwith a permanent, non-replaceable filter; without the complexity ofhi-voltage electronics or easily damaged electrostatic cells.

Salient components of the system 100 include the wash mechanism 130,which is comprised of a looping copper manifold 131 with fixed highpressure wash nozzles 132 (FIGS. 2, 8) to directly wash the stage Ifilter 120. A continuously running fogger assembly 110 configured tospray monodisperse fog droplets is positioned at the inlet 104 of thesystem 100 and serves to maximally reduce the temperature of theincoming particulate airflow/waste airstream. This results incondensation of some of the gas phase pollutants (VOCs and sVOCs)contained in the waste airstream and their subsequent collection ontothe stage I filter 120. Additionally, a small surplus of water, presenton the stage I filter 120 as a thin film due to those fog droplets whichhave not evaporated before contacting the stage I filter 120, is used toeffect removal, by solubilization and subsequent drainage, of anysoluble and polar particle and gas phase pollutants that are in thewaste airstream. Advanced oxidation processes (AOPs) are activated byinjecting oxidants into the fog created by the fogger assembly 110,which serve to decompose the susceptible target compounds in the wasteairstream.

Referring again to FIG. 1, pollution control system 100 includes ahousing 102 which houses a series of filters between an inlet 104 and anoutlet 170, at which an exhaust fan 180 creates an airflow path todischarge the commercial cooking exhaust (waste airstream) emitted fromthe commercial kitchen cooking ventilation hood to the outsideatmosphere. The pollution control system 100 would be installeddownstream of a commercial kitchen cooking ventilation hood (not shownfor purposes of clarity).

The airflow contaminated with cooking emissions (i.e., waste airstream,shown by arrows in FIG. 1) may be subject to a fogger assembly 110 atinlet 104, in which fog nozzles 112 spray a plurality of monodisperse, 1micrometer sized fog (minute water) droplets into the incoming airflowvia the action of a pump 145 drawing from a cold water source. Thesemonodisperse fog droplets mix with the air and evaporate to maximallyreduce the waste airstream temperature. The reduction in temperature ofthe waste airstream can be 40 degrees F. or more. This in turn resultsin greater numbers of particulates being collected in all of the stagesof the downstream filters 120, 140, 150. The effects of fogger assembly110 will be explained in further detail hereafter.

The stage 1 filter 120 is a washable metal filter which filters outparticles down to a size of 1 micrometer on a size-based (tested to ASTM2519 and published) increasing efficiency. The stage I filter 120 has areactor core (i.e. the center) which increases mixing of the wasteairstream with the fog droplets resulting in optimized mechanicalfiltering principles to remove particle pollutants (such as grease andsmoke) in the waste airstream, and optimized solubilization and removalby drainage into a drain 185 of soluble and polar particle and gas phasepollutants in the waste airstream, and dramatically increases thelifetime of the stage II filter 140 and the stage III filter by catchingall the grease in the waste airstream. The entire solubilization processand the acceleration of the AOPs (which are initialized as soon as theactivated ozone contacts the waste airstream) all take place within thereactor core (i.e., the interior) of the stage I filter 120 where themixing is maximized. Any particle and gas phase pollutants (i.e.,particulate matter, semivolatile and volatile organic compounds (sVOCsand VOCs)) that have not been removed from the waste airstream by thestage I filter 120 continue on into second annular space 125 to befiltered out by the stage II filter 140. The system 100 has slanteddrain pans 103 both before and after the stage I filter 120 for properdrainage into the drain 185.

The stage II filter 140 removes particulate matter at a second smallerparticulate cut size than the stage I filter 120. The stage II filter140 can be comprised as a rigid type filter resistant to water vapor ora bag-type filter. Both filter types are rated MERV 15 in accordancewith ASHRAE standard 52.2. Both filter types are proprietary withregards to their construction, moisture resistance, low pressure drop,and/or the stitching of a natural fiber material (such as wool) to asynthetic filter media which serves to both remove some VOCs as well aslengthen the life of the synthetic filter media. The airflow and anyparticles (including the condensed particle pollutants resulting fromcondensing a portion of the gas phase pollutants in the waste airstreamvia the fogging process), and gas phase pollutants such as sVOCs andVOCs not removed from the waste airstream by the stage II filter 140continue on into second annular space 135 to be filtered out by a stageIII filter 150.

The stage III filter is configured to remove sub-micron particlesremaining in the waste airstream after passing through the stage IIfilter 140, including any condensed particle pollutants. The stage IIIfilter 150 is constructed of a proprietary oil mist media which is ratedat a 99 DOP efficiency (removes up to 99% of 0.3 micrometer-sizedparticulates) but results in a performance that is substantially at thelevel of a HEPA filter (99.97% removal of 0.3 micrometer-sizedparticles). However, this stage III filter 150 has a longer lifetime andcosts significantly less than a HEPA filter. The airflow with anyremaining submicron particulate matter and sVOCs and VOCs that has notbeen removed by the stage III filter 150 continue on into third annularspace 155 to either be exhausted at outlet 170, or to be optionallyfiltered out by a stage IV filter 160 (filter bank(s)). Filter banks(s)in the stage IV filter 160 remove, by absorption, any remainingcondensed particle pollutants and the gas phase pollutants. The stage IVfilter 160 is included in system 100 if AOP is employed in the system100, so as to remove any remaining unreacted ozone in the system (i.e.,where VOC adsorption is required but atmospheric release of ozone is aconcern).

The optional stage IV filter 160 (shown in dotted line to denoteoptional) is configured to remove, by adsorption, sub-micron particleand gas phase pollutants remaining in the waste airstream after passingthrough the stage III filter 150. The optional stage IV filter 160 maybe a one or two pass filter system. The sorbents of the stage IV filtermay be comprised of a proprietary sorbent, an activated charcoalsorbent, or a blend of the proprietary sorbent and activated charcoal.Each of these sorbents will be discussed in further detail hereafter.

Accordingly, during normal commercial cooking operations, the hotexhaust collected in the commercial kitchen cooking ventilation hood isducted and drawn into the inlet 104 of system 100 by a UL 762 kitchengrease exhaust fan 180. The contaminated or waste airstream passes overstage I (120), stage II (140) and stage III (150) filters in sequence,and if included, a stage IV filter (160) consisting of one or two passes(one or two filter banks) of sorbent filters. Each filter in the firstthree filter stages I-III removes a size-dependent fraction of theparticulate component of the exhaust (the other component in the wasteairstream being gaseous, which would be removed by solubilization in thestage I filter, adsorption in the wool of the stage II filter andadsorption by the stage IV sorbent). All of the captured emissions aresubject to decomposition via the AOP oxidation process. All particleremoval efficiencies are described as MERV or DOP ratings according toASTMF 2519, ASHRAE 52.2 or Military standard 282 respectively. Forsystem 100, the respective efficiency ratings are as follows:

-   1. STAGE I—EFFICIENCY 58% @ 3 μm and 92% @ 5 μm (ASTM F 2519)-   2. STAGE II—MERV 15 (ASHRAE 52.2) with an optional natural fiber    layer stitched on-   3. STAGE III—(95-99) DOP (Military standard 282)

After the cooking operations cease, the wash operation begins. The washoperation is performed to remove the grease accumulated on the stage Ifilter 120. The wash operation consists of opening wash and detergentsolenoids by the wash control system (WCS) 195 and activating thedetergent pump 175, also done from the WCS 195. As shown in FIG. 1, hotwater with a specially formulated detergent 177 is pumped into the washmechanism 130. The distance from the washing surface is carefullycalculated to effect full coverage of the four square foot (2′×2′)filter area of the stage I filter 120. The detergent 177 is allowed tosoak and emulsify the accumulated grease on the filter 120 surface,after which a rinse cycle is commenced. Next, a five minute drip drycycle is commenced. The system 100 has slanted drain pans 103 bothbefore and after the stage I filter 120 for proper drainage into a drain185. This wash and rinse cycle is then repeated. After these first twocycles are completed, the exhaust fan 180 is activated for one hour todry the stage I filter 120.

FIG. 2 is a front portional view of part of the pollution control systemto show a fogger assembly in more detail; FIG. 3 is a plan view of anexample high pressure nozzle installed on a collar that is positioned ona stainless steel tube according to the example embodiment; and FIG. 4is a picture of a pump used for the fogger assembly 110 according to theexample embodiment. Referring to FIGS. 2-4, the fogger assembly 110utilizes the process of injecting a fine fog of monodisperse,equal-sized 1 micrometer aerosols (e.g., droplets) to effect evaporativecooling of the exhaust airstream. With this sized droplet, a maximalcooling of the waste airstream at the inlet 104 can occur. Thetemperature drop depends on the psychometric parameters of theairstream. Through this process of subjecting the incoming wasteairstream emitted from the kitchen ventilation hood to the fog dropletssprayed therein from fogger assembly 110, three objectives may beachieved. First, there is maximal cooling of the waste airstream so asto condense out susceptible VOCs and sVOCs (gas phase pollutants) thathave boiling points that are above the newly lowered psychometricairstream temperature due to the fog droplets evaporating in and coolingthe waste airstream. These compounds condense into the solid phase andare subsequently removed by filtration. Second, by increasing the numberof particles as described above, the particle sizes are grown throughagglomeration and hence can be removed earlier and/or more easilycleaned by the stage I and II filters 120, 140. Third, by having anexcess of fog droplets and a thin film of water on the surface of thestage I filter 120, the excess water resulting from those fog dropletswhich do not evaporate before contacting the stage I filter 120, thiscan effect solubilization of the highly and moderately polar compounds(I.e. polar particle and gas phase pollutants dissolvable in water)found in the emission profile, which are removed from system 100 via thedrain 185. Accordingly, the fogger assembly 110 sprays a fog ofmonodisperse droplets to mix with the incoming waste airstream so as toachieve psychrometric saturation of the waste airstream, evaporativecooling of the airstream, and condensation of susceptible gas phasepollutants in the airstream (those gas phase pollutants having boilingpoints above the new lower temperature of the cooled waste airstream)into condensed particle pollutants that may be easily removed by thefilters (stages I through IV).

To incorporate this technology, during standard filtering for cookingoperations (i.e., during non-wash times), the fogger assembly 110 makesuse of a high pressure pump 145 and a fog nozzle 112 configuration thatgenerates a fog of equal-sized 1 micrometer fog droplets to exploit thephysico-chemical properties of condensation and solubility to increasethe total mass of emissions removed from the airstream by the stage Ifilter 120. The number of fog nozzles 112 utilized is calculated usingpsychometric principals and is specific to the cooking processesoccurring under the kitchen hood and associated duct temperature.

The equipment includes a plurality of high-pressure fog nozzles 112 anda fogger pump 145, which may be a MicroCool pump for example. Threenozzles 112 are distributed vertically on each side of the air inlet 104through vertical stainless steel tubing 114 and the MicroCool RapidOrientation Collar (ROC) mounting system, which employs special collars113 that slips over the tubing 114 and includes sealing rings that makea pressure tight seal against the outer wall of the tubing 114,permitting the nozzle 112 to be rotated thereon at any desired angle.Each nozzle 112 can be closed with an integral closure screw ifnecessary for psychometric reasons.

The vertical stainless steel tubing 114 is joined at the top of theinlet 104 outside of the housing 102 and then connected by additionalstainless steel tubing to the fogger pump 145, which draws on the coldwater source. The nozzles 112 are pointed so that their spray pattern116 is directed into the incoming contaminated cooking exhaust air. Adistance of four feet within housing 102 between the fogger assembly 110and stage I filter 120 is utilized to effectively slow down the air andensure that the fog droplets are evaporating and the waste airstream isreaching water vapor saturation and maximum evaporative cooling.

The fogger pump 145 is activated by a signal from the WCS 195 controlpanel and the cold water solenoid is opened from WCS 195. The functionof the pump 145 is to maintain 1000 psi water pressure to the nozzles112 by incorporating a variable frequency drive and pressure feedbackloops. The droplet size of droplets in the fog is maintained at aconsistent 1 micrometer size.

The frame on which the fogger pump 145 is mounted can accommodate up totwo inline (in series) devices: a pH boosting device (shown as element147 in FIG. 1) to boost the pH of the cold water source, and a diamondcrystal ozone filter cartridge (shown as element 149 in FIG. 1) forgenerating dissolved ozone, to be discussed hereafter. The devices 147and 149 thus comprise an Advanced Oxidation Process (AOP) dissolved gasgenerator 146. A provision is made for an inclusive reverse osmosissystem for trouble-free nozzle longevity when AOPs are incorporated intothe system.

The use of Advanced Oxidation Processes (AOPs) is an ideal approach totreat persistent water or air contaminants. AOPs can be understood asthe combination of two or more processes to generate or increase thenumber of hydroxyl radicals (.OH). The hydroxyl radicals contribute tothe oxidation of undesirable substances and have a considerably higheroxidation potential compared to other oxidants.

Once the fog droplets are evaporated the hydroxyl radicals and theactivated ozone immediately react to decompose all susceptibleoxidizable substances. The high degradation performance and the quickreaction kinetics of this process are the formula for success when itcomes to eliminating numerous persistent substances.

Hydroxyl radicals are the foundational component of Advanced OxidationProcesses (AOPs). AOPs are initiated upon contact of activated ozonewith the waste airstream so as to decompose particle and gas phasepollutants within the waste airstream in the air as well as in all ofthe filter stages I through IV. It is thus offered as an option formaximal odor control and filter life within system 100. It is offered asan option for both wash (with wash mechanism 130) and non-wash pollutioncontrol systems. For the system 100 with wash mechanism 130, it may beinjected into the inlet 104 of the system 100 in one of two ways: namelyas dissolved activated ozone for AOPs via the AOP dissolved gasgenerator 146 (comprising pH booster device 147, and the diamond crystalozone cartridge 149 that generates the activated ozone (comprised ofozone gas with a surplus of hydroxyl radicals (.OH)) into the cold watersource on its path to the fogging nozzles 112 of fogger assembly 110; ordirectly injected from a AOP free ozone gas generator 196 into the inlet104 as activated ozone gas via an ozone gas injection device, shown inFIG. 1 as an ozone wand 190, for example. Either way, upon contact ofthe activated ozone with the waste airstream within system 100, AOPswhich initiate therefrom serve to generate a set of oxidative cascadereactions that result in the destruction/decomposition of most of theorganic compounds found in the cooking emissions (i.e., wasteairstream). The reactivity of various organic compounds to undergooxidation is well studied and reaction rates and orders well known.These susceptible compounds may be individual compounds that are in theairstream, absorbed or adsorbed on particles that have been captured onthe stage I and II filters 120 and 140, or adsorbed onto the wool in thestage II filter 140 or sorbent filter bank(s) comprising the stage IVfilter 160 (the latter is a requirement to utilize this technology whenatmospheric dumping of fugitive or unused ozone in system 100 is aconcern).

For ozone injection with the fogging assembly 110, such may beaccomplished by installing the AOP dissolved gas generator 146, whichcomprises the pair of inline devices 147 and 149 as previouslydiscussed, into the incoming cold water line. The pH booster 147 isdesigned to raise the pH of the filtered cold water source by addingliquid NaOH into the water, which increases the amount of OH ions in thewater for subsequent generation of hydroxyl radicals for AOPs, so that amaximum amount of hydroxyl radicals (.OH) can be formed for the AOPs.The ozone cartridge 149 may be embodied as a Solid Synthetic DiamondElectrode cartridge and is provided to generate dissolved ozone gas tomix with the surplus hydroxyl radicals within the water so as toactivate the dissolved ozone within the water. Upon evaporation duringthe evaporative cooling process (due to the fog droplets released by thenozzles 112 of the fogger assembly 110), the activated ozone is releasedto initiate AOPs, which generate oxidation of the organic compounds inthe mixed air/fog waste stream and in all stages of the filters. Fornon-wash systems (i.e., systems without a wash mechanism 130), theactivated ozone for AOPs can only be injected in gas form via the AOPfree ozone gas generator 196 to the ozone wand 190, but is still highlyeffective.

FIG. 5 is a front view of an ozone injection device according to anexample embodiment; FIG. 6 is an end view of the ozone injection deviceof FIG. 5. System 100 is provided with an optional ozone injectiondevice in the form of ozone wand 190. Wand 190 is configured to receivea source of ozone directly from an external source of ozone, forexample, the AOP free ozone gas generator 196. In an alternativeembodiment, another or second ozone injection device could be placedafter the stage III filter 150; this is identified by injection point191 in FIG. 1.

Referring to FIGS. 5 and 6, wand 190 is a double walled stainless steeltube that spans the inlet 104 to system 100 and consist of a “blind”solid metal half 194 that faces the dirty air and a perforated “openhalf” 197 that allows the ozone to leave the annular space 115 and enterthe airstream. The inner tube 192, also made of stainless steel is asolid tube with a series of increasing hole diameters 193 designed todistribute the ozone evenly along the length of the tube and also toassure that the pressure ozone exceeds that of the ductwork staticpressure at the inlet 104 of system 100. The weight of ozone deliveredis calibrated based on the AOP free ozone gas generator 196 output andthe distribution pressure in the inner tube 192 and external to it inthe inlet 104. It is assumed that all ozone that leaves the inner tube192 effectively enters the airstream through the outer half 194 blindtube.

The wash control system (WCS) 195 has many functions. As examples, someof the functions of the WCS 195 include, but are not limited to:

-   -   1) Start and stop the exhaust fan 180 (and remote supply fan if        applicable);    -   2) Respond to a fire alarm condition by releasing fire        suppression chemical and if desired, water into the system 100,        shutting off remote supply fan and activating (if not already        on) the exhaust fan 180;    -   3) Control the wash cycle by activating the hot water solenoid,        detergent pump 175, and exhaust fan 180 in accordance with the        wash cycles described below:        -   a. 2 minute fan shutdown,        -   b. 30 second pre wash hot water warm up,        -   c. 2 minute wash with detergent,        -   d. 1 minute rinse,        -   e. 5 minute drip dry and drain,        -   f. Repeat step c thru e, and        -   g. 60 minute forced air dry;    -   4) Signal to activate the fogger assembly 110 solenoid and        fogger pump 145, if included as an option; and    -   5) Signal to energize the ozone filter cartridge 149 of AOP        dissolved gas generator 146, if included as an option.

FIG. 7 is a partial side view of the first and second stage filters toillustrate the wash mechanism in greater detail; FIG. 8 is a perspectiveview of the looping manifold and nozzles of the wash mechanism inrelation to the first stage filter. Referring to FIGS. 7 and 8, the washmechanism 130 is comprised of a looping copper manifold 131 whichincludes a plurality of fixed nozzles 132. Nozzles 132 are full conicalhigh pressure spray nozzles As best shown in FIG. 8, the stage I filter120 may comprise a metal frame 121 which retains a plurality of stackedfilter coil pack reactors 122 (“coil packs”) therein. Three coil packs122 are shown in FIG. 8, although two may be sufficient depending uponCFM requirements. The “s” or serpentine shape of the manifold 131provides three nozzle rows, each row containing a set of threeequally-spaced nozzles 132 to spray a mixture of hot water and detergent177 (via detergent pump 175) onto the surface of each of the three coilpacks 122 of filter 120. This nozzle configuration is only exemplary;different combinations of nozzles 132 may be used so long as thewater-detergent spray is evenly distributed on the surfaces of the coilpacks 122. As previously noted, the distance of the wash mechanism 130from the washing surfaces of the stage I filter 120 is carefullycalculated to effect full coverage of the four square foot (2′×2′)filter area of the stage I filter 120.

FIG. 9 is an example coil pack reactor used in one type of a stage Ifilter according to an example embodiment. FIG. 10 is another anddifferent style of stage I filter called the Cascade Filter with thereactor being the space within the filter and the air directed there bysmall slots. Both filters are nominally two inches thick and fit into a2 inch filter track with weep holes to allow the removed grease to drainto the sump.

The first example filter for use as the stage I filter 120 is theVeritech® filter, with its plurality of stainless-steel coil packs 122(2 or 3 coil packs depending on the air volume). The Veritech filter isa stainless steel coil pack filter which has a higher collectionefficiency (a 60% removal for particle size 3 microns) than analternative stage I filter type referred to as the Cascade filter, and agreater surface area for solubility interaction. The coil pack 122 isshown in FIG. 9 and several of these coil packs (two or three coil packsin vertical relation, depending on the CFM requirement) are stacked in atypical installation into a metal filter frame 121 (FIG. 8) to beinstalled as a stage I (24″×24″×2″) filter 120. The reactor (i.e.,interior) within the coil packs 122 of the Veritech filter is where theextensive mixing and solubilization of the polar compounds found in thewaste airstream occurs entirely and where the advanced oxidationprocesses (AOPs) are accelerated via extensive mixing, and where thefinal degree of the condensation takes place as well. Accordingly, theuse of a Veritech filter as the stage I filter 120 is desirable so that,maximum solubilization, maximum chance of oxidation of compounds, andmaximum temperature drop in the waste airstream can occur, (i.e., mixingwithin the reactors of the coil packs 122 to enhance, solubility,oxidation and evaporative cooling).

The Veritech filter coil pack is disclosed and described in EP0857508 toVan Nierkirk, published Aug. 12, 1998 (filed Oct. 2, 1998) and entitled“Separation Apparatus”, the entire contents of which are herebyincorporated by reference herein. An alternative filter for stage I isbuilt off the coil pack 122′ shown in FIG. 10, which is offered byFranke® as the Cascade™ grease filter. This filter has a 50% removalefficiency for particle size 5 micrometers. The Franke® Cascade™ greasefilter coil pack is disclosed and described in U.S. Patent Appl. Pub.No. 20120247074 to Chmayssani et al., published Oct. 4, 2012 (filed Mar.29, 2012) and entitled “Double Helix Grease Filter”, the entire contentsof which are hereby incorporated by reference herein.

FIG. 11 is a partial front view of a stage II filter according to anexample embodiment, and FIG. 12 is a cross-section of the stage IIfilter of FIG. 11 showing material components thereof. Referring toFIGS. 11 and 12, the stage II filter 140 is provided by Safe AirService, LLC. Stage II filter 140 has a one-inch header 141 and a filterbag body designed as a plurality of pleats 142. Specifically, the stageII filter 140 consists of a double layer stitched media bag filter witha one inch header. FIG. 12 shows the material used to make the filter140 of FIG. 11. The material includes a natural fiber which in oneexample is a proprietary wool layer 143, which is attached (such as bystitching, heat sealing and/or adhesives) onto a MERV 15 synthetic media144, which in turn is attached to material which forms the outer surface145 of the filter 140. Wool is a hydrophilic in nature and thisfacilitates gas (VOC) removal by adsorption. A natural fiber such aswool also serves to wick any accumulated grease particles that havepassed through the stage I filter 120 away from the MERV 15 syntheticmedia 144 so as to significantly enhance the stage II filter 140'sreplacement lifetime. Accordingly, incorporation of a wool layer 143 ontop of the MERV 15 synthetic media 144 in the stage II filter 140 allowsthe filter 140 to now remove and retain a portion of the gases (VOCs)therein.

Another possible embodiment for the stage II filter 140 is a customizedMERV 15 box filter. This box filter is designed for a smaller unit andfeatures a very low pressure drop as well as a high resistance tomoisture.

FIG. 13 is a perspective front view of a stage III filter according toan example embodiment, and FIG. 14 is a cross-section of the stage IIIfilter internals of FIG. 13. Referring to FIGS. 13 and 14, the fibercross-section of the stage III filter 150 includes a high-impact plasticframe 151, a bead separator 152 and synthetic media 153, which is anoil-mist media. This provides an embossed oil mist media with adhesivebead separators, known as an “E-Pleat” technology pleat pack which isgenerally water resistant. The stage III filter 150 is unique in that itdoes not allow water to penetrate the filter and thus could be washed inanother embodiment of the system 100. This stage III filter 150 isdisclosed and described in FIGS. 33-34 of U.S. Pat. Appl. Pub. No.20120317940 to Ball et al., published Dec. 20, 2012 (filed May 24, 2012)and entitled “Non V-Bank Filter For Animal Confinement Facility”, theentire contents of the application being incorporated by referenceherein. The stage III filter 150 is constructed with a specialized oilmist media. This unique filter media was screened and tested under theSouth Coast Air Quality Management District (SCAQMD) PAR 1138 testingprotocol and demonstrated to be as efficient as a comparative HEPAfilter under real world char broiling of 20% fat hamburgers. The stageIII filter 150 with oil-mist media has a 99 DOP rating. Due to thenatural attraction of the oil-mist media to the oily composition of thebulk of the cooking emissions; this filter removes approximately thesame amount of particulate as a glass HEPA filter rated at 99.97%.

The stage IV filter 160 (filter bank(s)) is configured to remove, byadsorption, any condensed particle and gas phase pollutants remaining inthe waste airstream after passing through the stage III filter 150. Thestage IV filter 160 (filter bank(s)) is used when VOC adsorption isrequired (and mandated when ozone is injected into the system 100, whichneeds to be quenched prior to exiting outlet 170 to the atmosphere) andmay be either 2-inch flat panels arranged in a “V” configuration” orarranged in V-shaped cassettes, or, when a double pass configuration ischosen, the flat panels and the cassettes. The weight range for eitherof these is 12-25 pounds for service convenience. One sorbent materialto be used in these filter bank(s) may be composed of a new proprietarysorbent called TechZorb-RH. TechZorb-RH is a hydrophobic syntheticzeolite which is specifically compounded to function well in highhumidity environments (such as a fog environment), and removes VOCs byadsorption in the high relative humidity environment. In an example(within a fog environment) where the stage IV filter 160 is configuredas a two pass system, the first pass filter may include the TechZorb-RHas the sorbent and the second pass filter may include activated charcoalas the sorbent.

A variation of TechZorb has been developed for non-fogging systems(where fogger assembly 110 is not employed). Typically, a stage IVfilter 160 in this configuration may be a two-pass configuration (firstpass filter including TechZorb as the sorbent, second pass filter havingactivated charcoal as the sorbent. This TechZorb variation is also ahydrophobic synthetic zeolite, but it is formulated for lower humidityand higher adsorption capacity to catch the fraction of the VOCs thatthe activated charcoal does not catch (in a non-fog environment).

Two passes of sorbent for the stage IV filter 160 assure greater odorreduction and halves the frequency of replacement, and is recommendedfor freestanding units, as opposed to self-contained re-circulatingunits (ventless hoods), as space does not allow this configuration. Whena double pass configuration (2 filters in series) of sorbents is used(and recommended to quench any fugitive ozone), a second pass of bondedcarbon panels is recommended.

FIG. 15 is a drawing of a recirculating (ventless) kitchen exhaust hood,FIG. 16 is a side view of the drawing of FIG. 15, and FIG. 17 is a blockdiagram of a pollution control system according to an example embodimentconfigured for the recirculating (ventless) kitchen exhaust hood ofFIGS. 15 and 16. Another application for the removal of cookingemissions involves the use of the same filtration technologies in whatis termed a recirculating hood. Here, the exhaust collected over non-gascooking appliances are run through a series of filters and thendischarged back into the kitchen space. One distinct and tremendousadvantage of this technology is that the dramatic cooling of the hotexhaust air (by fogger assembly 110) allows the technology to be listedfor electric char broilers.

Referring to FIGS. 15 through 17, all of the above describedtechnologies can be implemented in the aforementioned ventlessrecirculating hood device. These consist of a regular kitchen exhausthood (FIG. 15) that has a filtration mechanism (FIG. 17) contained inthe housing above the hood filters shown in FIGS. 15 and 16 and thatdischarges the air back into the kitchen space after filtering it. Aminiaturized version of the fogger pump 145 has been developed for thisapplication, although not shown for reasons of brevity.

Again, the described technologies lead to reduced filter cost and moreefficient filtration through fogging and ozone introduction. Inclusionof one inch activated charcoal sorbent panels 160 is mandatory toeliminate fugitive ozone from entering the indoor kitchen space. Theserecirculating hoods must pass a specific UL 710B standard to certifythat they achieve the required particulate emission reduction. Also,these hoods are never used for gas-fired appliances since they representa risk of carbon monoxide poisoning.

FIG. 18 is a block diagram of a mechanical filter-based pollutioncontrol system according to another example embodiment. FIG. 18 includesmany of the same components as in FIG. 1; thus only the differences arediscussed in detail. FIG. 18 illustrates a system 100′ without a foggerassembly 110 and without a wash mechanism 130. As there is no filterwashing, the stage I filter 120 may be composed of a less expensivedisposable synthetic media for filtering grease and particles in thewaste airstream. An example may be a synthetic filter with an efficiencyrating of MERV 6-10. The efficiency of the stage I filter 120 isselected so as to approximate the same filter change frequency as thatof the stage II filter 140 (so they can be replaced at the same time).The stage II filter 140 may have the same construction as in FIG. 1, awool layer attached to a MERV 15 synthetic media for removing particleand gas phase pollutants remaining in the waste airstream after passingthrough the first stage filter 120. The stage III and IV filters 150,160 may also be similar as described with respect to FIG. 1, where thestage III filter includes an oil-mist media therein for removingsub-micron particle pollutants remaining in the waste airstream afterpassing through the stage II filter, and where the stage IV filter 160removes, by adsorption, sub-micron particle and gas phase pollutantsremaining in the waste airstream after passing through the stage IIIfilter 150.

In this embodiment, since there is no fogger assembly 110 and no washmechanism 130, the means to inject activated ozone within the housing toinitiate AOPs upon contact with the waste airstream, so as to decomposeparticle and gas phase pollutants of the waste airstream in the firstthrough fourth stage filters, is met by incorporating the AOP free ozonegas generator 196 and an ozone injection device such as ozone wand 190into system 100′. The activated ozone for AOPs can only be injected ingas form via the AOP free ozone gas generator 196 to the ozone wand 190.

Accordingly, the pollution control system 100 as heretofore describedemploys ozone in advance oxidation processes (AOPs) to maximize thenumber of hydroxyl radicals generated, so as to decompose particlestrapped in filter stages I-IV, to decompose solubilized VOCs (gaspollutants) through mixing in the stage I filter 120, to decomposeadsorbed VOCs trapped in the wool layer 143 of the stage II filter 140,and to decompose any remaining VOCs adsorbed in the stage IV filter 160.

The stage II filter 140 with its wool layer 143 can lengthen the life ofthe stage IV filter 160 sorbent because some VOCs that normally wouldreach the stage IV sorbent can actually be adsorbed and held in the woolof the stage II filter 140. This segregation also facilitates greateroxidative destruction of all adsorbed gas phase pollutants via AOPs inboth locations because of the lesser density of adsorbed compoundsspread through the total volume of media or sorbent (i.e., the volume ofwool fibers in the stage III filter 140 and the volume of the sorbentmaterial in the stage IV filter 160)). Further, the stage III filter 150enhances oxidative destruction of adsorbed particles because of thegreater amount of smaller particles that are retained. Specifically, itsoil-mist media increases the efficiency of the filter 150, so as toremove approximately the same amount of particulate as a glass HEPA99.97 filter, due to the attraction of the oil-mist media to theemission compound (oil).

Yet further, a pollution control system 100 including a combination ofthe fogger assembly 110, stage II filter 140 having the wool/syntheticmedia material construction, and stage III filter 150 with the oil-mistmedia substantially reduces filter replacement costs while maximizingemission removal.

The example embodiments being thus described, it will be obvious thatthe same may be varied in many ways. Such variations are not to beregarded as departure from the example embodiments, and all suchmodifications as would be obvious to one skilled in the art are intendedto be included in the following claims.

I claim:
 1. A mechanical filter-based air pollution control system forremoving particle and gas phase pollutants in a waste airstreamexhausted from commercial cooking operations, comprising: a housinghaving an inlet and an outlet, an exhaust fan attached to the outlet fordrawing the waste airstream into the inlet and through the housing tothe outlet and discharging to the outside atmosphere, a fogger assemblyarranged within the housing at the inlet and connected to a cold watersource for spraying equal-sized 1 micrometer droplets to mix with theincoming waste airstream so as to achieve psychrometric saturation ofthe waste airstream, evaporative cooling of the airstream, andcondensation of a portion of gas phase pollutants in the waste airstreaminto condensed particles, a first stage metal filter arranged within thehousing and downstream of the fogger assembly for filtering particlepollutants, and solubilizing and removing by drainage polar particle andgas phase pollutants in the waste airstream, a second stage filterarranged within the housing and downstream of the first stage filter,the second stage filter including a wool layer attached to a MERV 15synthetic media therein for removing particles, including the condensedparticles, and gas phase pollutants remaining in the waste airstreamafter passing through the first stage filter, and a third stage filterarranged within the housing and downstream of the second stage filter,the third stage filter including an oil-mist media therein for removingsub-micron particle including the condensed particle pollutantsremaining in the waste airstream after passing through the second stagefilter.
 2. The system of claim 1, further comprising: a wash mechanismarranged in the housing in facing relation to a front of the first stagefilter, the wash mechanism including a manifold supporting a pluralityof spray nozzles thereon, the manifold supplying a mix of heated waterfrom a hot water source and detergent to the nozzles for periodicallywashing surfaces of the first stage filter to remove grease therefrom.3. The system of claim 1, further comprising: a fourth stage filterarranged within the housing and downstream of the third stage filter forremoving, by adsorption, condensed particle and gas phase pollutantsremaining in the waste airstream after passing through the third stagefilter.
 4. The system of claim 3, wherein the fourth stage filter isconfigured as a two pass filter system, the first pass filter includinga sorbent composed of a hydrophobic synthetic zeolite compounded to beeffective in high humidity, and the second pass filter includingactivated charcoal as the sorbent.
 5. The system of claim 3, wherein thefourth stage filter is configured as a single pass filter system, thefilter having a sorbent including a blend of hydrophobic syntheticzeolite and activated charcoal.
 6. The system of claim 3, furthercomprising: injection means to inject activated ozone, which comprisesozone with a surplus of hydroxyl radicals, within the housing toinitiate advanced oxidation processes (AOPs) upon contact of theactivated ozone with the waste airstream so as to decompose particle andgas phase pollutants within the waste airstream and retained in thefirst through fourth stage filters.
 7. The system of claim 6, whereinthe injection means for injecting ozone includes an AOP dissolved gasgenerator which comprises a pH boosting device for raising the pH of acold water source supplied thereto to increase an amount of OH ions inthe water for subsequent generation of hydroxyl radicals for AOPs, and aozone filter cartridge in series with the pH boosting device forgenerating dissolved ozone that mixes with the raised-pH water to createactivated ozone, the water with activated ozone being injected into thefogger assembly to produce droplets that initiate the AOPs.
 8. Thesystem of claim 1, wherein the portion of the gas phase pollutantscondensed into condensed particle pollutants are those gas phasepollutants having a boiling point greater than the cooled wasteairstream temperature.
 9. A mechanical filter-based air pollutioncontrol system for removing particle and gas phase pollutants in a wasteairstream exhausted from commercial cooking operations, comprising: ahousing having an inlet and an outlet, an exhaust fan attached to theoutlet for drawing the waste airstream into the inlet and through thehousing to the outlet and discharging to the outside atmosphere, adisposable, synthetic first stage filter with an efficiency rating ofMERV 6-10 for filtering particles in the waste airstream, a second stagefilter arranged within the housing and downstream of the first stagefilter, the second stage filter including a wool layer attached to aMERV 15 synthetic media therein for removing particle and gas phasepollutants remaining in the waste airstream after passing through thefirst stage filter, a third stage filter arranged within the housing anddownstream of the second stage filter, the third stage filter includingan oil-mist media therein for removing sub-micron particle pollutantsremaining in the waste airstream after passing through the second stagefilter, a fourth stage filter arranged within the housing and downstreamof the third stage filter for removing, by adsorption, sub-micronparticle and gas phase pollutants remaining in the waste airstream afterpassing through the third stage filter, and injection means to injectactivated ozone, which comprises ozone with a surplus of hydroxylradicals, within the housing to initiate advanced oxidation processes(AOPs) upon contact of the activated ozone with the waste airstream soas to decompose particle and gas phase pollutants within the wasteairstream and retained in the first through fourth stage filters,wherein the fourth stage filter quenches any fugitive or unused ozoneremaining in the system.
 10. The system of claim 9, wherein theinjection means for injecting ozone includes an AOP free gas generatorexternal to the housing which generates ozone gas and is connected to anozone injection device arranged within the housing at the inlet, theozone gas injected directly into the waste airstream at the inlet viathe ozone injection device.
 11. The system of claim 9, wherein thefourth stage filter is configured as a two pass filter system, the firstpass filter including a sorbent composed of a hydrophobic syntheticzeolite and the second pass filter including activated charcoal as thesorbent.
 12. The system of claim 9, wherein the fourth stage filter isconfigured as a single pass filter to include a sorbent composed of ablend of a hydrophobic synthetic zeolite and activated charcoal.
 13. Thesystem of claim 12, wherein the hydrophobic synthetic zeolite sorbent iscompounded to catch a fraction of the gas phase pollutants that theactivated charcoal sorbent does not catch.
 14. A mechanical filter-basedair pollution control system for removing particle and gas phasepollutants in a waste airstream exhausted from commercial cookingoperations, comprising: a housing having an inlet and an outlet, anexhaust fan attached to the outlet for drawing the waste airstream intothe inlet and through the housing to the outlet and discharging to theoutside atmosphere, a fogger assembly arranged within the housing at theinlet and connected to a cold water source for spraying fog droplets tomix with the incoming waste airstream so as to condense gas phasepollutants in the airstream to condensed particles, a first stage metalfilter arranged within the housing and downstream of the fogger assemblyfor filtering particle pollutants, and solubilizing and removing bydrainage polar particle and gas phase pollutants in the waste airstream,a wash mechanism arranged in the housing in facing relation to a frontof the first stage filter, the wash mechanism including a manifoldsupporting a plurality of spray nozzles thereon, the manifold supplyinga mix of heated water from a hot water source and detergent to thenozzles for periodically washing surfaces of the first stage filter toremove grease therefrom, a second stage filter arranged within thehousing and downstream of the first stage filter for removing particleand gas phase pollutants remaining in the waste airstream after passingthrough the first stage filter, a third stage filter arranged within thehousing and downstream of the second stage filter for removingsub-micron particle including condensed particle pollutants remaining inthe waste airstream after passing through the second stage filter, afourth stage filter arranged within the housing and downstream of thethird stage filter for removing, by adsorption, condensed particles andgas phase pollutants remaining in the waste airstream after passingthrough the third stage filter, and injection means to inject activatedozone within the housing, which comprises ozone with a surplus ofhydroxyl radicals, to initiate advanced oxidation processes (AOPs) uponcontact of the activated ozone with the waste airstream so as todecompose particle and gas phase pollutants within the waste airstreamand retained in the first through fourth stage filters, wherein thefourth stage filter quenches any fugitive or unused ozone remaining inthe system.
 15. The system of claim 14, wherein the first stage filterfilters particle pollutants in the waste airstream including grease andsmoke down to a 1 micrometer size.
 16. The system of claim 14, whereinthe fog droplets are equal-sized 1 micrometer droplets.
 17. The systemof claim 14, wherein the second stage filter includes a wool layerattached to a MERV 15 synthetic media therein.
 18. The system of claim14, wherein the third stage filter includes an oil-mist media therein.19. The system of claim 14, wherein the fourth stage filter isconfigured as a two pass filter system, the first pass filter includinga sorbent composed of a hydrophobic synthetic zeolite and the secondpass filter including activated charcoal as the sorbent.
 20. The systemof claim 14, wherein the injection means for injecting ozone includes anAOP dissolved gas generator which comprises a pH boosting device forraising the pH of a cold water source supplied thereto to increase anamount of OH ions in the water for subsequent generation of hydroxylradicals for AOPs, and a ozone filter cartridge in series with the pHboosting device for generating dissolved ozone that mixes with theraised-pH water to create activated ozone, the water with activatedozone being injected into the fogger assembly to produce droplets thatinitiate the AOPs.